FYI we just finished 3 months around central and western australia in our 17.58-3. It was an awesome holiday - the kids loved it - as did the parents! We had a few issues:
- pump failed just as we were about to cross the nullarbor - good timing! it was a simple replacement in port lincoln tho - done in about 10 mins at the jayco service dealer.
- a few of the drawer locks failed - might be worth carrying some spares (about $10 each).
- there seems to be a supply issue of gas from one of the bottles - it works some of the time, but you can't trust it to keep the fridge cold - but that said, using gas nearly every day and running the fridge on gas for a few weeks, we used less than a bottle in 3 months - impressed with that
- a few screws worked their way loose - watch the screws on your awning around the edge of the tube - if you lose them then it will unwind itself and you'll never get it back to the way it should be (i looked one day in Kakadu and there was only one screw left there holding it - and it was already halfway out!) - and those screws are the ones that need the square head to turn - and no one had the tool...
- the black edging above the tyres threatened to fall off in the first week - so I glued them back on
- the table tried to fall off the wall (it happens to everyone with this model!)
- the curtains on the bunks tried to fall off (the screws they used to hold the curtain box on are a joke...)
- the hinge on the cupboard above the sink came out (the screws they use are tiny!) - fixed just with some larger screws
There were probably a few other small things, but pretty much everything I could fix myself. Watch the plug for the fridge/van power supply under the bunk - it can work its way out when driving on corrugations. But we had no serious structural issues despite doing a bit of off-road driving. We had some friends travelling at the same time in an expanda and they did a fair bit of off road (mereenie loop, oodnadatta track, gibb river rd) and they had a wheel come off, lost water, power, gas, power again etc - basically a lot of stuff went wrong!). So i guess if you treat it well it will treat you well!
enjoy your trip - i am jealous! ours was one of the best things i have ever done - saw some amazing stuff and had some awesome experiences!